As I built my new computer and researched hardware I realized I was falling behind in my technical knowledge. I had to sort out a number of things to be able to intelligently decide which was best technically and for the money. This article is on the aspects of storage devices and proves a lot of information on SSD’s.
I wrote Hardware: Disk Performance Compared to provide just performance information. I was concerned with performance of Second Life™ an OpenGL based game/virtual world. Here I’ll get into the complications behind getting good performance, cover how to make comparisons for the best buy, and provide information on how it affects Second Life performance.
To get the most for your money you are going to have to be able to see through the advertising hype. So, as you read specs and try to make comparisons you’ll run into a variety of designators for data transfer rates and storage volume. They are all worded to make a product sound good.
Let’s start with the upper case ‘B’ and the lower case ‘b’, which have specific meanings. In the simplest use 1B = 8b, or 1 byte equals 8 bits. A bit is a 0 or 1. A byte is a total of eight 0’s and 1’s. (For more on this see Online Conversion, a tutorial.)
In some places we see 6GBps used to mean 600Mbps. This can look like B = 10b. Here because they are talking about data moving from storage devices through the transfer path they add in the data overhead of 2b (bits) for error correction and 1B does equal 10b in THEIR math. They are taking some liberties in their ad copy. One often has to CAREFULLY look at the numbers and determine the context intended to understand the size of a ‘byte’ being discussed.
In some ways the B’s, G’s, and M’s are misleading in how they are used. It is easy to make a case for that being deliberate. The actual data being moved is 8b/10b = 0.8 * 6000Mb raw data = 4,800Mbps actual usable by you data. But, manufactures like the bigger number and they are literally moving 6Gbps. It just isn’t all your data that is getting reported. They assume the knowledgeable user will infer their true meaning. I suspect they know a whole bunch of people won’t.
Unless you are comparing devices and protocols on a way technical level thinking in terms of data rates as 6GBps verses 4.8GBps doesn’t matter much. Consider. Is 6GBps SATA III faster than 3GBps SATA II? Yes. Is 4.8GBps faster than 2.4GBps? Yes. The difference wouldn’t change the take away that SATA III is faster than SATA II regardless of which numbers you use. Nor when comparing prices does it really change what we decide.
The take away here is to be sure you use the same measures for your comparisons. Also understand these are the THEORETICAL values of maximum performance which is seldom achieved.
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